Shea Butter is a butter extracted from the kernel of Butrospermum parkii. This plant, also referred to as Vitellaria paradoxa, is native to Africa. The term butter describes a material that is a solid at room temperature, but melts at about 40° C. Chemically, the butter is a triglyceride conforming to the following structure
wherein Rx, Ry and Rz each have one of the following compositions:
R GroupCommon NameRange (%)Typical (%)C11H23Lauryl0.1-2.00.2C13H27Myristyl0.5-2.01.0C15H31Cetyl2.0-6.04.0C17H35Stearyl25.0-50.035.0C17H33Oleyl40.0-60.059.0C17H31Linoleyl0.5-1.00.8
The average composition of Ry is different than Rx and Rz, the latter two being similar. The Ry moiety contains predominantly the unsaturated C18 group (oleyl) while Rx and Rz contain predominantly the saturated C18 group (stearyl). Differences between internal (Ry) and terminal (Rx, Rz) substitution are seen in natural products, but not in synthetic molecules produced in the laboratory.
The high levels of stearyl and oleyl groups in mild-processed shea butter and its alkoxylate derivatives make them of particular interest in the personal care industry. While other raw materials used in personal care products have these species, the compounds of the present invention have significantly high concentrations of unsaponifiables, which posses highly desired antioxidant, ultra-violet radiation protection, and free-radical scavenging properties. MPSB alkoxylates of the present invention typically contain from about 5% to about 15% by weight of unsaponifiables. In contrast, other butters commonly used in personal care products have less than 2% unsaponifiables. For example, coca butter (from Theobroma cacao) averages 0.4% unsaponifiables and Illipe butter (from Shorea stenoptera) averages 1.1%.
As described in greater detail below, the novel mild-processed shea butter alkoxylates of the present invention are produced by an ethenification reaction of MPSB with ethylene oxide, propylene oxide or mixtures thereof under specific mild-processing conditions. By “mild processed” is meant processes that do not remove or otherwise diminish the amount or potency of active ingredients, particularly highly desired unsaponifiables. In the present invention, mild processing is employed both at the time of harvesting and initial extraction (creating mild-processed shea butter) and during subsequent preparation of its alkoxylate derivatives. These processes result in materials containing unexpectedly high amounts unsaponifiables, notably antioxidants.
Polyoxyethylene glycol (PEG)/Polyoxypropylene glycol (PPG) esters are described in the prior art. U.S. Pat. No. 5,917,070 teaches polyoxyalkylene glycol esters prepared by the reaction of polyoxyalkylene glycol with meadowfoam oil as a triglyceride, as a fatty acid or as a methyl ester. The meadowfoam PEG/PPG esters are described as having good oxidative stability which is attributed to the specific carbon chain distribution of meadowfoam oil. These prior art compounds differ, however, from the alkoxylated mild-processed shea butters of the present invention in which ethylene oxide, propylene oxide and mixtures are inserted into mild-processed shea butter through an ethenification reaction.
Ethoxylated shea butter is listed in the International Dictionary of Cosmetic Ingredients (10th Edition), published by the Cosmetics, Toilteries and Fragrance Association. Ethoxylated shea butter having about 75 moles of ethylene oxide per mole of glyceride is commercially available under the tradename Lipex™ 102 E75 from Karlshamns AB (Karlshamn, Sweeden). This material is extracted with hydrocarbon solvents. Ethoxylated shea butter is also commercially available form Oils By Nature (Cleveland, Ohio) and KIC Chemicals, Inc. (Armonk, N.Y.).
The novel alkoxylates of the present invention are water-soluble emollients that not only not only condition and soften skin and hair, but also deliver antioxidants (present in the unsaponifiable fraction of mild-processed shea butter) in a heretofore unachievable manner.